Implantable stimulation devices deliver electrical stimuli to nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators (DBS) to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a Spinal Cord Stimulation (SCS) system, such as that disclosed in U.S. Pat. No. 6,516,227. However, the present invention may find applicability with any implantable medical device or in any implantable medical device system.
As shown in FIG. 1, a SCS system typically includes an Implantable Pulse Generator (IPG) 10, which includes a biocompatible device case 12 formed of titanium, for example. The case 12 typically holds the circuitry and battery 14 necessary for the IPG to function. The IPG 10 is coupled to electrodes 16 via one or more electrode leads 18 (two of which are shown). The electrodes 16 are coupled to the IPG 10 at one or more lead connectors 20 fixed in a header 22, which can comprise an epoxy for example. In the illustrated embodiment, there are sixteen electrodes, although the number of leads and electrodes is application specific and therefore can vary. In a SCS application, two electrode leads 18 are typically implanted on the right and left side of the dura within the patient's spinal cord. The proximal ends of the leads 18 are then tunneled through the patient's flesh to a distant location, such as the buttocks, where the IPG case 12 is implanted, at which point they are coupled to the lead connector(s) 20.
FIG. 2A shows a front view of an external controller 50 for communicating with the IPG 10, and FIG. 2B shows the external controller 50 and IPG 10 in cross section. Two coils (antennas) are generally present in the IPG 10: a telemetry coil 24 used to transmit/receive data via a wireless communications link 75 to/from the external controller 50; and a charging coil 26 for charging or recharging the IPG's battery 14 using an external charger (not shown). These and other components 25 necessary for IPG operation are electrically coupled to a circuit board 23. The telemetry coil 24 can be mounted within the header 22 of the IPG 10, or can be located within the case 12 as shown.
The external controller 50, such as a hand-held programmer or a clinician's programmer, is used to send or adjust the therapy settings the IPG 10 will provide to the patient (such as which electrodes 16 are active, whether such electrodes sink and source current, and the duration, frequency, and amplitude of pulses formed at the electrodes, etc.). The external controller 50 can also act as a receiver of data from the IPG 10, such as various data reporting on the IPG's status and the level of the IPG 10's battery 14. The external controller 50 is itself powered by a battery 52, but could also be powered by plugging it into a wall outlet for example. A user interface similar to that used for a cell phone is provided to operate the external controller 50, including buttons 54 and a display 58. The external controller 50 also includes a telemetry coil 56. These and other components 59 necessary for IPG operation are electrically coupled to a circuit board 57.
Wireless data transfer between the IPG 10 and the external controller 50 typically takes place via magnetic inductive coupling between coils 24 and 56, each of which can act as the transmitter or the receiver to enable two-way communication between the two devices. A Frequency Shift Keying (FSK) protocol can be used to send data between the two coils 24 and 56 via link 75. Although use of an FSK protocol in legacy systems is discussed below, use of this protocol is not universal, and other protocols employing different forms of modulation can be used to communicate between an external controller and an IPG, as one skilled in the art understands. Telemetry of data can occur transcutaneously though a patient's tissue 80.
Historically, external medical devices such as external controller 50 have been built by the manufacturer of the IPGs, and thus such external devices are generally dedicated to only communicate with such IPGs. The inventor has realized that there are many commercial mobile devices, such as mobile cell phones and multi-function tablets, that have the necessary configurable hardware and software to function as an external controller for an IPG or other implantable medical device. Using such mobile devices as external controllers for an implantable medical device would benefit both manufacturers and end users: manufacturers would not need to build dedicated external controllers that end users must buy, and end users could control their IPGs without the inconvenience of having to carry additional custom external controllers.
However, there are problems with this solution. Mobile devices are often configured with necessary hardware and software to communicate with other devices using short-range protocols, such as Bluetooth, Bluetooth Low Energy (BLE), Near Field Communication (NFC), Zigbee, and WiFi, as well as by using long-range cellular telephony protocols, any of which can be used to ultimately wireless connect the mobile device to the Internet or other network. While such communication channels allow for communication with an implantable medical device, they also render mobile devices less secure than traditional dedicated external controllers, particularly because they are prone to cyber attack, to computer viruses or malware, or to other intentional forms corruption. The multi-functional nature of mobile devices also makes them more prone to unintentional corruption, as their complicated nature may simply cause them to function improperly, even if they haven't been intentionally corrupted. Thus, if mobile devices are used as medical devices to communicate with implantable devices, there is an increased risk that the implantable medical device could be mis-programmed and potentially injure a patient.
Further, external medical devices are governed by FDA regulations such as 21 C.F.R. 820, which set forth requirements for class III medical devices such as external controllers. These rules require levels of safety and security that a mobile device may not meet for the reasons just explained.